Jpn. Pat. Appln. KOKAI Publication No. 2008-234470 (Patent Document 1) discloses a tough panel in which ends of the lines of a pair of insulating-film side electrodes are connected to ends of insulating-substrate side lines by a conductive adhesive. The touch panel has a slit near a corner of the insulating film and near a connecting portion that electrically connects ends of the insulating-film side wiring and the insulating-substrate side wiring.
The slit of the insulating film prevents stress concentration in the above connection portions, when the touch panel is heated to cause deformation of the insulating film and the insulating substrate due to the difference in coefficient of thermal expansion between the film and the substrate. Namely, the slit functions to absorb deformation of the insulating film to thereby prevent stress concentration in the connection portions. As a result, detachment of the connection portions due to the stress caused by thermal expansion is prevented.
However, since the insulating film expands in all planar directions, stress occurs in, for example, connection portions between the insulating film and another substrate and between the above-mentioned lines. Namely, stress occurs in the two connection portions serving as the insulating film connection portions, whereby the above-mentioned detachment problem occurs. In particular, in the case of a large touch panel, the deformation amount of the insulating film relative to the substrate increases, which means that the problem of detachment between the insulating film and the substrate inevitably becomes conspicuous.